The present invention relates to a liquid level control apparatus for controlling or detecting the liquid level in a water tank employed, for example, in an ice making machine.
FIG. 1 of the accompanying drawings shows schematically a structure of a well known liquid level control apparatus, by way of example. In the drawings, a reference numeral 1 denotes a container or tank which is provided with a guide member 3 disposed above the maximum height which the liquid level 2 within the tank 1 can attain. The guide member 3 supports a vertically slidable leg member 4. A slidable sleeve 4a is integrally formed at a base end portion of the leg member 4.
Mounted on the leg member 4 at the lowermost free end thereof is a float 6 which is vertically movable in response to variations or changes in the liquid level between the maximum level 2 and a controlled liquid level 5.
In the well known liquid control apparatuses, the guide member or column 3 is disposed above the maximum height so that the liquid level can attain, as mentioned above, a view to preventing the guide column 3 from being immersed within the body of liquid when the liquid level rises up to the maximum height 2, because otherwise high viscosity of liquid, contaminants or the like would be deposited on the slidably contacting surfaces of the guide column 3 and the slidable sleeve 4a, causing erroneous level detection and hence erroneous operation or mulfunction. Even so, well known liquid level cotrol apparatuses suffer the drawbacks mentioned below:
(1) When the difference between the maximum level 2 and the controlled liquid level 5 is selected to be large, the length of the float supporting leg member 4 has to be increased. Additionally, the leg member 4 has to be imparted with adequate rigidity for assuring a smooth relative movement of the leg member 4 along the guide column notwithstanding the bouyancy exerted on the float 6. This provides an additional factor contributing to an increase in weight of the leg member 4.
(2) In order that the arm 4 can move up and down smoothly in response to the bouyancy exerted on the float 6 according to the change in the liquid level, it is necessary to provide sufficient clearance between the slidable sleeve 4a and the guide column 3. However, due to such clearance, the leg member 4 tends to be inclined at large angles relative to the longitudinal axis of the guide member 3, making it difficult or even impossible to control or monitor the liquid level with acceptable accuracy.
In the above noted construction, the well known liquid control apparatuses can respond to changes in the height of liquid surface only after a delay and difficulty is encountered in performing detection or control of the liquid level with high accuracy, giving rise to problems.